Fuel cell battery

ABSTRACT

Several fuel cells, each comprising a metal electrode in a gaspermeable envelope electrode with a catalytically effective inner surface, are juxtaposed to form a battery and are separated by solid spacers which are carried on an interposed partition or project directly from confronting outer surfaces of adjoining envelope electrodes to form channels for the admission of air or oxygen to the respective cells.

C United States Patent [151 3,650,839 Lang et al. 1 Mar. 21, 1972 [54]FUEL CELL BATTERY 3,432,353 3/1969 Von Krusenstierna et al. ..136/863,061,658 10/1962 Blackmer ...136/86 [72] .1 f? f Renal 3,442,714 5/1969Matsuno ...136/86 mamas 3,462,307 8/1969 Voorhies et al ...136/86 [73]Assignee; Yardney International Corp, New Y rk 3,476,609 1 1/1969Gelting et al. 1 36/86 Primary Examiner-Allen B. Curtis [22] Flled: July1968 Attorney-Karl F. Ross 21 A LN 741,634 1 1 PP 57] ABSTRACT 52 us. Cl..l36/86 several fuel cells each metal elwmde a [51] Int CL Helm 29/04permeable envelope electrode with a catalytically efi'ective [58] Fieldh 136/86 inner surface, are juxtaposed to form a battery and areseparated by solid spacers which are carried on an interposed 56]References Cited partition or project directly from confronting outersurfaces of adjoining envelope electrodes to form channels for theadmis- UNITED STATES PATENTS sion of air or oxygen to the respectivecells. 3,378,406 4/1968 Rosansky 136/86 1 Claims, 6 Drawing Figures FUELCELL BATTERY Our present invention relates to a fuel-cell battery with aplurality of juxtaposed cells each-comprising a metallic inner electrodein a gas-permeable outer envelope electrode, e.g., as describedincommonly assigned application 31,873 filed May 4, 1970 which is acontinuation of Ser. No. 664,151 filed 21 Aug. 1967, now abandoned, byRenato Di Pasquale and Frank Solomon.

In such fuel cells it is necessary to ensure that a depolarizing gas,such as air or oxygen, can reach the interior of each cell through theinterstices of the permeable envelope in sufficient quantities tomaintain a high rate of interaction with the electrolyte therein, suchinteraction being promoted by a catalyst coated onto the inner surfaceof the envelope or incorporated in the usually dielectric (e.g.,resinous) matrix thereof so as to be available at the interface betweenthe gas stream and the liquid electrolyte. With the metalliccounterelectrode constituted by a consumable zinc plate, for example,the catalyst may consist of carbon particles admixed with Teflon in themanufacture of the sheet material from which the envelope electrode isformed, the ratio of carbon to Teflon increasing throughout thethickness of the envelope from its outer to its inner surface so thatthe outer surface is relatively hydrophobic while the inner surface isrelatively hydrophilic; as likewise described in the above-identifiedapplication, the carbon particles may be metalized for improvedcatalytic action.

The need for making available a copious supply of gas conflicts with therequirement for compactness of the assembly of juxtaposed cells.Moreover, the tendency of the organic envelope to swell upon contactwith the electrolyte further militates against a close juxtaposition ofthe cells, especially where these cells are serially interconnected sothat short-circuiting intercell contact must be avoided.

The general object of our present invention is to provide an improvedcell assembly of the type referred to which satisfies the aforestateddesiderata of ensuring an adequate gas supply to each cell, affording acompact construction and preventing internal short circuits.

These objects are realized, pursuant to a feature of our presentinvention, by the provision of a solid partition between each pair ofadjoining cells, this partition establishing separate gas channels forthe two cells and being provided with spacer formations which engage theouter surfaces of the associated cell envelopes to maintain apredetermined width of each channel. It is also possible to providethese spacer formations directly on the confronting outer envelopesurfaceson opposite sides of the interposed partition.

In accordance with another important aspect of this invention, theinterposed spacing means forms part of a structure which, together witha pair of rigid frame members encircling the top and the bottom of theenvelope electrode of each cell, insures a precise dimensioning of theoverall cell assembly irrespective of any changes in the wall thicknessof the envelopes. This effect is independent ofthe presence of absenceof a solid partition; without such partition of insulating material,however, the separation of the cells may have to be made somewhatgreater, or the intercell spacers may have to be more densely arrayed,if the risk of shorting between cells is to be positively excluded. Thetwo frame members of each cell may or may not be interconnected by meansother than the envelope electrode. The lower frame member may begenerally trough-shaped, forming a closed bottom to hold the liquidelectrolyte inside the cell; the upper frame member may be open or maybe a partly closed cap with one or more apertures for the introductionof the electrolyte and for the escape of evolving gases.

The invention will be described in greater detail with reference to theaccompanying drawing in which:

F lG.'1 is a top view of a cell assembly according to the invention;

FIG. 2 is a cross-sectional view of the assembly of FIG. 1, taken on theline 11-11 thereof;

FIG. 3 is a fragmentary perspective view of one of the cells shown inFIGS. 1 and 2;

FIGS. 4 and 5 are fragmentary perspective views generally similar toFIG. 3, illustrating modifications; and

FIG. 6 is a fragmentary cross-sectional view of two adjoining cellsembodying the construction of FIG. 5.

The electrochemical energy generator shown in FIGS. l-3 is an air/zincbattery 10 composed of a multiplicity of substantially identical cells10a, 10b, 10c, 10d juxtaposed under pressure within a yoke 1 11.

As particularly illustrated for the cell 10b in FIG. 3, each cellcomprises a negative zinc electrode 12 wrapped in a permeable orsemipermeable separator sheet 20 and positioned upright in an envelopeelectrode 13 of polymeric sheet material which is pervious to air and iscomposed of a mixture of a hydrophobic resin and a catalytic agent. Thissheet material may be prepared, as described in the aforementionedapplication Ser. No. 664,151 and in another commonly assignedapplication, Ser. No. 601,546 filed 14 Dec. 1966, now abandoned, byAllen Charkey and Renato Di Pasquale, by admixing pure or metal-platedcarbon powder with an agueous emulsion of Teflon to form a paste, dryingthis paste at a temperature of about 60 to 250 C. and then curing thedry mixture by heating it to a temperature of about to 350 C. in thesubstantial absence of air, together with a thermally destructiblefiller such as a glycol which vaporizes at the curing temperaturewithout leaving an undesirable residue in the resulting sinter body;this curing step may also be used to laminate the porous structure,rolled or pressed into sheet form, onto a metallic support such as anickel grid 14 imbedded between two such sheets and joined to a terminallead 15. The weight ratio of plain or metalized (e.g., platinumcoated)carbon to Teflon may range from about 10:1 on the inner envelope surfaceto about 1:1 on the outer surface, the latter surface being thus highlyhydrophobic whereas the inside of the envelope is hydrophilic andcatalytically active.

Output lead 15, during operation, delivers a positive voltage withreference to the potential of a negative lead 16 connected to aconductive grid 17 imbedded in zinc plate 12. The prismatic airelectrode 13, 14 is connected at the top and the bottom to a pair ofmembers 18', 18" of frame rigid dielectric, preferably plastic material,e.g., polystyrene. The upper frame members 18' are shown as upwardlyopen collars while the lower frame members 18" are closed-bottom troughspreventing the outflowof a liquid electrolyte 21 (e.g., an aqueous KOI-Isolution) present within each cell.

In accordance with an important feature of our invention, each cell isseparated from an adjoining cell by a rigid, plateshaped partition 19which, resting against shoulders 23 (FIG. 3) of frame members 18, 18",defines therewith a peripherally open channel for the admission of adepolarizing gas (here specifically air) to the outer surface of thepervious envelope 13. The width of this air channel tends to decreaseduring operation as the material of envelope 13 begins to swell underthe action of the electrolyte 21 present within the envelope 13. Inorder to maintain a desired minimum width for each air channel, weprovide the partition 19 with formations 22 bearing upon the outersurface of each adjoining envelope 13; as specifically illustrated,these formations are generally hemispherical projections integral withthe partition and distributed over both its major surfaces. The plate 19may consist of plastic or other dielectric material similar to oridentical with that of the frame members 18', 18".

While each of the'inner cells 10b, 10c is flanked by a pair of suchpartitions 19, the two outermost cells 10a and 10d are confronted on theoutside by end plates 19', 19" having projections 22 only on theirinnersurfaces. These end plates 19', 19" bear upon the outermost pairs offrame members 18', 18" whereas each'partition 19 is bracketed betweentwo pairs of such frame members. Thus, the frame members 18', 18" andthe plates 19, 19, 19" form a stack of predetermined dimensionssubdivided into a plurality of upwardly, downwardly and laterally opencompartments for the several cells 10a-10d. The invariable width of eachcompartment, corresponding to the frame width w (FIG. 1), is sufficientto accommodate an envelope electrode 13 and a counterelectrode 12 withinitial clearance for the admission of electrolyte and lateral space forthe flow of air to the outer envelope surfaces, the width of thislateral space being determined by the depth of the projections 22 whichsubstantially equals the thickness of frame members 18, 18" at theirshoulders 23.

In holding the air-permeable sheet 13 at a predetermined distance fromthe adjoining dielectric plates 19, 19', 19", the spacers 22 also tendto maintain the inner surface of the swollen sheet in contact with thezinc plate 12 through the intermediary of separator 20, therebyresisting any substantial deformation of this electrode duringdischarge.

The flow of air or oxygen through the peripheral gaps defined byshoulders 23 may be promoted, if necessary, by pumps or other force-feedmeans not shown. The assembly shown in FIGS. l-3 may be placed in anouter receptacle, not illustrated, and may of course be enlarged orreduced as to the number of its cells. The leads 15, 16 of adjoiningcells may be connected in a series circuit. though a parallel connectionis also possible; owing to the interposition of insulating partitions19, there is no danger of internal short circuits due to a formation ofelectrolyte bridges between the several cells.

In FIG. 4 we have shown part of a modified cell assembly according tothe invention wherein the upper frame members 118, clamping a dielectricpartition 119 between their corner shoulders 123, form partly closedcaps with apertures 118a which serve for the filling of the cell withelectrolyte and for the venting of its interior. This Figure alsoillustrates the possibility ofleaving the surface of plate 119 smoothand providing the intercell spacers in the form of beads 122a, l22b onconfronting surfaces of the envelopes 113a, 113b of adjoining cells. Inthis embodiment, partitions 119 need not be as strong and rigid as theplates 19 of the preceding Figures.

FIGS. and 6 depict a further modification with omission of the solidintercell partitions. Spacers 222 are shown as vertical stringerscemented onto an edge of an upper frame member 218a (as onto well as aparallel edge of the corresponding lower frame member, not shown) whilebearing under pressure, e.g., from a yoke such as the one illustrated at11 in FIGS. 1 and 2, upon corresponding frame members of an adjoiningcell, one such frame member being seen at 21% in FIG. 6. Thetransversely spaced stringers 222 are formed with vertically spacedenlargements 222a, 222b which rest against the confronting outersurfaces of envelopes 213a, 213b, their height h (FIG. 6) beingsubstantially equal to the thickness of the frame members 2180, 218b.

Frame members l8, 18" etc., could also be metallic, with or withoutexternal plastic (e.g., epoxy) coating.

Other modifications readily apparent to persons skilled in the art,e.g., as regards the structural details of the cell frames and thecompositions of the electrodes, are also intended to be embraced withinthe spirit and scope of our invention as defined in the appended claims.

We claim:

1. A fuel-cell battery comprising a plurality of cells each including anenvelope electrode of gas-permeable sheet materia], a liquid electrolytein said envelope electrode and a counterelectrode immersed in saidelectrolyte, said envelope electrode having a catalytically efiectiveinner surface for promoting interaction between said electrolyte and agas penetrating said sheet material; a solid partition of insulatingmaterial interposed between each pair of adjoining cells, said partitionforming two separate gas channels alongside the outer surfaces of theenvelope electrodes of said adjoining cells and being provided withprojections spacedly bearing upon said envelope electrodes; and a pairof rigid frame members projectingly surrounding each envelope electrodeat the bottom and the top thereof, respectively, and bearing uponopposite surfaces of the interposed partition at vertically spacedlocations, at least one of said frame members of each pair being partlycut away with formation of a pair of horizontally spaced shouldersseparated by a gap and maintaining jointly with said projections apredetermined clearance between said envelope electrodes and saidpartition for making said envelope electrodes accessible to said gasthrough the spaces between said frame members and through said gap whilemaintaining said envelope electrodes insulated from each other.

